Encouraged by several, successful "big" reports by other members, I decided to go a bit bigger: 480GB SSD Drive, with about 320Gb content on it.

The hardware worked well, got recognized, played music, etc. BUT: I did encounter a strange behavior with folders "randomly disappearing."
The behavior was not consistent so I decided to test more methodically.

Wiped the drive clean and filled it with "fake" music. I picked a 1Mb song and replicated it under a carefully-designed folder structure, which proves, likely, that the BMW song indexer has a 16 bit limit (65,536 songs).

The structure I created had:
16 Genres in the root (4 bits)
64 Artists under each Genre (6 bits)
8 Albums under each Artist (3 bits)
16 Songs under each Album (4 bits)

Total: 17 bits, 131,072 songs, occupying, as expected, about 120GB on the drive.

Each song has a unique file name and a corresponding ID3 tag specifying its "location." A file would look like "10.G06.AR18.AL06.mp3"

I connected the drive with the test data and something very interesting happened: for the first few minutes, while the indexer was active, I couldn't browse by artist/album, etc. - only through folders. And I was able to browse the ENTIRE tree and play it. I saw all the Genres/Artists/Album, etc.

BUT, once the indexer finished (took a few minutes there...) several folders disappeared. I could only see some of the Genres, some of the Artists under them and some of the Albums under each (visible) artist.

I couldn't seem to find any consistent "pattern" to which folders remained and which disappeared.

I wonder if any other people noticed a similar behavior with larger collections.
I am going to repeat this experiment with half of the collection removed (16 bits, 65536 songs). I will report any findings once I have them.

For the record, the car is a 2014 F30, with MN-003.001.002 / TN-003.001.002 (which appears to be the latest version as of today).

Even if I'm right and there is indeed an indexer limit, I wonder why such a limit prevents simple folder browsing, as such activity requires no index.

Great work! I am using a 2tb HDD to store about 37k songs. I am finding some strange behavior as well. For example voice search does not work. When I first tested it using only 2 artists, it worked fine. But now when I say "search artist" the car responds with something like "loading media" then nothing happens.

My original media folder had about 55k songs. But with all the "secondary files" (JPG for covers, M3Us, thumbs.db from windows) the number of actual files got jacked up to almost 70k.
So if you noticed strange behavior with your collection, try to perform an actual file count.

Chopped down the song list from 17 to 16 bit: 65,536 songs.
Same behavior: after indexing the whole tree, some folders disappear.

Unless I'm doing something wrong in my test procedure, this is quite disappointing. I realize that to many people this may seem like a hard limit to reach, but for many who amassed a larger collection over the years, this can be an annoying limitation.

Also, with modern computers (even ones from the last 5 years), this should be very easy to index 100,000 files. I would venture to say even a million.

I'll see if I can chop the collection a bit more (no pun intended), to find out (at least roughly) what is the hard limit on collection size.

It may be safe to assume you can't voice-search while the indexer is active.
The question, as you put it, is why the indexer is active again after everything got indexed previously (without the media reinserted).

Here's my theory: the same issue we're observing with "folders disappearing" is actually an error condition with the indexer running out of memory. The error condition likely leaves the collection flagged as non-indexed (partially?) so when the car is restarted at a later time, the indexer attempts to...index again.

Again - only theory, but I may learn more if I manage to get the collection down to a size that avoids the error. I'll see if the problem you're reporting (I'll call it "redundant indexing") also disappears in that case.

Agreed...why does the car seem to re-index or have to load the library every time I start the car? You are probably right in that BMW cheaped out on memory. The head unit probably has to do a bunch of memory swapping.

All I know is that this worked really well when I only had 2 artists and about 120 track on my HDD! LOL!

Well I hope the reindexing is unrelated to max tracks because mine does a reindex every time I start the system after sitting overnight. I think iDrive reboots after that amount of time and it may trigger the indexing. I only have around 3-4K tracks at the moment. It's just part of my full library.

I've been playing with this voice search issue more. So my problem right now is that sometimes I can do a voice search on Artist only (after the car re-indexes my HDD after each startup, about 5 mins). As I understand, once I do an artist search, the car should respond with "select category". The categories should be Genre, Album, Tracks, etc.

For some artists, I can search on Artist then Album, Genre, etc. Other Artists, I get a "feature not supported" error immediately after I do the Artist voice search. Probably related, but I cannot initiate a search on Album at all.

You can just place all the music files in the root of the drive, and shuffle all. There is no limitation in size (that I've found). I have close to 3000 songs and it shuffles them all.

Makes loading new songs easier as well. You just copy them in there, and no mucking with playlists. (Assuming you just want to listen to everything, and don't have specific lists for different genres, etc).